1. Field of the Invention
The present invention relates to an image forming apparatus that includes an open/close detecting unit that detects sheet feeder cassette units.
2. Description of the Related Art
In recently years, saving energy is loudly advocated in society and is in demand with regard to image forming apparatuses. Therefore, recent image forming apparatuses provide a sleep mode that restricts energy consumption by supplying power to the minimum required functions. For example, the image forming apparatus includes sheet feeder cassette units for storing recoding papers, where each sheet feeder cassette unit is provided with an open/close sensor for detecting an open/closed state of the sheet feeder cassette unit. In sleep mode, power is supplied to the minimum required function parts such as the open/close sensor, a circuit engine board that is a control circuit including a CPU (Central Processing Unit), which receives a detecting signal from the open/close sensor, or the like. This approach intends to save energy in the image forming apparatus. For example, Japanese Patent Applications No. 2009-184076 and No. 2008-216829 propose methods of conserving energy based on the sleep mode.
However, in the related art described above, power needs to be supplied to multiple open/close sensors for respectively detecting open/closed states of each sheet feeder cassette units. In such a case, the power consumption in a sleep mode increases with an increase in the number of sheet feeder cassette units. Furthermore, in the case of an optional sheet feeder cassette unit apparatus that is attached to the main body of an image forming apparatus as optional equipment, another control circuit having a CPU is included for controlling the optional sheet feeder cassette unit apparatus separately from the main body of the image forming apparatus. Further, the optional sheet feeder cassette unit apparatus includes an engine substrate that includes a CPU separately from the main body of the image forming apparatus. The CPUs control operations in the optional sheet feeder cassette unit apparatus via serial communication between the main body of the image forming apparatus and the optional sheet feeder cassette unit apparatus. For restarting the optional sheet feeder cassette unit apparatus from sleep mode by opening/releasing the sheet feeder cassette unit, power needs to be maintained to both the control circuit of the main body of the imaging apparatus and the engine substrate of the optional sheet feeder cassette unit apparatus. For this purpose, power needs to be supplied to the engine substrate and the open/close sensor of the optional sheet feeder cassette unit apparatus even in sleep mode. In this manner, the image forming apparatus according to the above related art requires power supply to the sheet feeder cassette unit apparatus even in sleep mode for detecting the open/closed state of the sheet feeder cassette unit. This increases power consumption of the image forming apparatus of the related art.
The present invention takes into consideration the issues described above. For example, one of the objects of the present invention is to reduce power consumption of an image forming apparatus for detecting a state of being open/closed when a sheet feeder cassette unit is in a sleep mode.